open up run (press windows key and R) and type in 'services.msc' (without quotes). Find something like 'Bluetooth' in the list, open properties. Go to dependancies tab, and find what is in the top box. Find in the main list what is in the top box and make sure those services are not disabled
If you are still receiving : ERROR: Unable to start Bluetooth Stack Services?
Have you recently run a registry program for example Registry Booster 2?
If so then this may be the cause and suggest you restore to an earlier saved point from the RB backup.
I had the same issue and despite contacting Dell support and checking internet forums, the problem still occurred until I recognized it was the registry program new settings that was causing the start up problem.
I restored on the Registry problem to the back up and the issue has gone. I can even locate my BT TRAY.
Microsoft support don't seem to have an idea. Nothing new there.